The present invention generally relates to an electromagnetic relay.
Conventionally an electromagnetic relay is proposed in FIG. 18 and FIG. 19. In the electromagnetic relay, a movable block 6 with a movable stand 7 being retained between a pair of leaf springs 8, 8 secured at its one end is operated in accordance with the energization and deenergization of an electromanget block 5 in the opposite directions of the leaf springs 8, 8 (in FIG. 19, arrow mark m, n directions) so as to bring a movable terminal 6a into contact againt a stationary terminal 3a secured onto the base 1. The movable terminal 6a is supported through a support stand 6a' on the movable stand 7. The electromagnet block 5 has a yoke 5c, a coil terminal (in FIG. 18, the coil is not shown) disposed in a spool 5b with an iron core 5a being inserted into it.
The electromagnetic relay substantially consists of a base 1, a seal plate 2, terminal blocks 3, 3, a metallic fixture 4 for positioning the one-ends of the leaf springs 8, 8 in the groove portions 1a, 1a of the base 1, a movable contact piece to be securely press fitted into the movable stand 7, a permanent magnet 6c to be grasped by a pair of movable iron pieces 6b, 6b so as to be securely press fitted into the movable stand 7.
In the electromagnetic relay, the leaf spring 8 is secured onto a projection 7a disposed on the side wall of the movable stand 7, and the support stand 6a' is press fitted from below into the through hole 7b, and secured with a bonding agent The leaf spring 8 and the support stand 6a' are respectively secured onto the movable stand 7 by the separate means.
Therefore, there is a problem that the number of assembling jobs of the movable block 6 is more, and the productivity thereof is worse.
Also, since the leaf spring 8 is not secured onto the movable stand 7 with the bonding agent, the adherence property with respect to the movable stand 7 is worse so as to shake the movable stand 7, with a problem that the operating characteristics become unstable.
Also, in the electromagnetic relay, since the leaf spring 8 is made approximately uniform in the sectional shape, it is deformed into a semielliptic shape in accordance with the movement of the movable stand 7. As shown in FIG. 19, the leaf spring 8 on this side moves with the distance S1 from the one end portion 8a thereof to the basic portion of the positional projection 7a being provided as a distance between the support points when the movable block 6 is operated in the direction of an arrow mark m direction. But when the movable block 6 is restored in the arrow direction n direction, the leaf spring moves with the distance S2 from one end portion 8a of the leaf spring 8 to the contact portion 8b to come into the angular portion of the movable stand 7 being provided as a distance between the support points, so that the distance between the support points becomes different when the movable block moves in the arrow mark m direction, and when it moves in the arrow mark n direction. Therefore, the spring constant changes, causing unbalance in the spring elasticity of the leaf spring. The same thing can be said about the case of the other leaf spring 8. Thus, the movable block 6 does not move in parallel. Also, the movable block 6 moves in an inclined condition by the twisting of the leaf springs 8, 8, a time lag is caused in the switching operation of a contact because of the uneven contact of the movable contact type 6a, with a problem that the operation characteristics of the electromagnetic relay are not good.
Further, such an electromagnetic relay as in the conventional embodiment fixedly crimps the leaf springs 8, 8 onto a pair of positional projctions 7a, 7a to be projected sidways from both the side faces of the movable stand 7 so as to grasp them. As shown in FIG. 18, when the mobable block 6 is operated in an arrow mark m direction, the leaf spring 8 on this side moves with the distance S1 from one end portion 8a thereof to the basic poriton of the positioning projection 7a being provided as the distance between the support points. When the movable block 6 is restored into the arrow mark n direction, it moves with the distance S2 from one end portion 8a of the leaf spring 8 till the contact portion 8b comes into contact against the angular portion of the movable portion 7 being provided as the distance between the support points, so that the distance between the support points in the reciprocating moving operation becomes different (S1.noteq.S2) even when the distance S3 between the terminals 8a, 8a is equal to the distance S4 between the contact portions 8b, 8b. Therefore, the spring constant of the leaf spring 8 changes so as to cause the unbalance in the spring force. The same thing can be said about the case of the other leaf spring 8. As a result, the movable block 6 does not move in parallel, but moves in an inclined condition. Since the time lag is caused in the switching operation of the contact with the movable contact piece 6a being uneven in contact, a problem is provided in that the operation characteristics of the electromagnetic relay are not good.
Also, such an electromagnetic relay as in the covnentional embodiment secures the leaf springs 8, 8 through the thermal crimping onto a pair of positional porjections 7a, 7a to be projected sideways from both the side faces of the movable stand 7 so as to grasp them, so that the mounting direction and the moving direction are the same. Therefore, as the fixing strength in the moving direction is low, the leaf springs 8, 8 are likely to be separated from the moving stand 7.
Further, since the leaf springs 8, 8 are likely to be floated in the thermal crimping operation, and are often crimped thermally in a condition where they are not adhered on the movable stand 7, the given amount of elastic force is hard to obtain, so that the dispersion may be likely to be caused in the operating characteristics.
Also, as shown in FIG. 18, when the movable block 6 is operated in the arrow mark m direction, the leaf spring 8 moves with the distance S1 from one end portion 8a thereof to the basic portion of the positional projection 7a being provided as the distance between the support points. When the movable block 6 is restored in an arrow mark n direction, it moves with the distance S2 from one end portion 8a of the leaf spring 8 to the contact portion 8b to come into cotnact against the angular portion of the movable stand 7 being provided as the distance between the support points, the distance between the support points in the reciprocating movement is different. Thus, the elastic contact varies so as to cause the unbalance in the spring force through the leaf spring 8. The same thing can be said about the case of the other leaf spring 8. As a result, the movable block 6 does not move in parallel, but moves in an inclined condition. Since the time lag is caused in the switching operation of the contact with a movable contact piece 6a being uneven in contact, the operating characteristics of the electromagnetic relay is not good.
Further, conventionally in the electromagnetic relay, an electromagnet on the base has a through hole communicating from the top face thereof to the bottom face thereof provided in the base, with a projection portion provided from the spool or the like of the electromagnet being engaged into the through hole, and the projection portion being heated, melted for a fixing operation. Namely, the projection portion has both a function as a fixing member and a function as a positioning member.
However, since the projected portion is heated, melted so as to deform the shape thereof, the electromagnet is slid out of the normal position of the base, and the distance between the electromagnet and the other member such as movable member, the contact goes wrong, with a problem that the operation characteristics of the electromagnetic relay are dispersed.